Inlays and onlays / implant dentistry course/ implant dentistry course


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Inlays and onlays / implant dentistry course/ implant dentistry course

  2. 2. Contents  Introduction  Definitions  Cast Metal Restorations  Indications and Contraindications  Advantages and Disadvantages  Tooth Preparation  Restoration  Onlays
  3. 3.  Tooth-Coloured Restorations  Indirect Composites  Ceramic Restorations  Indications and Contraindications  Advantages and Disadvantages  Tooth Preparation  Restoration  Repair of restorations  CAD-CAM based restorations  Inlay retained Bridges  Strength and Longevity of Inlays and Onlays  Review of Literature
  4. 4. Introduction
  5. 5.  Sometimes, a tooth is treatment planned to be restored with an intracoronal restoration, but the decay or fracture is so extensive that a direct restoration, such as amalgam or composite, would compromise the structural integrity of the restored tooth by possibly undermining the remaining tooth structure or providing substandard opposition to occlusal forces.  In such situations, an indirect gold or porcelain inlay restoration may be indicated.  When an inlay is used, the tooth-to-restoration margin may be finished and polished to such a super-fine line of contact that recurrent decay will be impossible.
  6. 6.  It is for this reason that some dentists recommend inlays as the restoration of choice for pretty much any and all filling situations.While these restorations might be ten times the price of direct restorations, the superiority of an inlay as a restoration in terms of resistance to occlusal forces, protection against recurrent decay, precision of fabrication, marginal integrity, proper contouring for gingival (tissue) health, ease of cleansing and many other aspects of restorative quality offers an excellent alternative to the direct restoration. For this reason, some patients request inlay restorations so they can benefit from its wide range of advantages even when an amalgam or composite will suffice.The only true disadvantage of an inlay is the higher cost.
  7. 7.  Additionally, when decay or fracture incorporate areas of a tooth that make amalgam or composite restorations essentially inadequate, such as cuspal fracture or remaining tooth structure that undermines perimeter walls of a tooth, an onlay might be indicated. Similar to an inlay, an onlay is an indirect restoration which incorporates a cusp or cusps by covering or onlaying the missing cusps.  All of the benefits of an inlay are present in the onlay restoration.The onlay allows for conservation of tooth structure when the only other alternative is to totally eliminate cusps and perimeter walls for restoration with a crown.
  8. 8.  Just as inlays, onlays are fabricated outside of the mouth and are typically made out of gold or porcelain. Gold restorations have been around for many years and have an excellent track record.  In recent years, newer types of porcelains have been developed that seem to rival the longevity of the gold. Either way, if the onlay or inlay is made in a dental laboratory, a temporary is fabricated while the restoration is custom made for the patient. A return visit is then required to deliver the final prosthesis. Inlays and onlays may also be fabricated out of porcelain and delivered the same day utilizing techniques and technologies relating to CAD/CAM Dentistry.
  9. 9. Definitions  Inlay A fixed intracoronal restoration; a dental restoration made outside of a tooth to correspond to the form of the prepared cavity, which is then luted into the tooth.
  10. 10.  Onlay A restoration that restores one or more cusps and adjoining occlusal surfaces or the entire occlusal surface and is retained by mechanical or adhesive means.
  11. 11. Cast Metal Restorations
  12. 12.  These restorations are versatile and are especially applicable to Class II onlay preparations.  Class II inlay involves the occlusal and proximal surfaces of a posterior tooth and may cap one or more but not all the cusps.  The Class II onlay involves the proximal surfaces of the tooth and caps all of the cusps.
  13. 13. Materials Used  Casting alloys used  advantage  high tensile and compressive forces  valuble in restorations to rebuild most or entire occlusal surface.  Four distinct groups of alloys are used currently:  High gold alloys  Low-gold alloys  Pallidium-silver alloys  Base Metal Alloys
  14. 14.  The alternatives to high gold restorations have required modifications of technique or acceptance of reduced performance, most commonly in regard to decreased tarnish resistance and decreased burnishability.
  15. 15. History of Casting Alloys  In 1907,Taggart introduced the lost wax technique for the fabrication of cast inlay restorations in dentistry.  In 1950, resin veneers were developed for gold alloys.  In 1959, Porcelain Fused to MetalTechnique was introduced.  In 1971, Nickel based alloys as alternative to gold alloys.  1980s saw the introduction of All Ceramic Restorations.
  16. 16. Mechanical Properties of Dental Casting Alloys Alloy type Description Use I Soft Some inlays II Medium Inlays and Onlays III Hard Onlays, Crowns,Thick Veneer Crowns, Short span FPDs IV Extra-hard ThinVeneers Crowns, Long span FPDs, CPDs 1997/2002 ADA no. 5
  17. 17.  Classification according to composition: Noble Metal Content wt% Gold Content wt% High Noble 60 40 Noble At least 25 - Predominantly Base metal Less than 25 - 1984
  18. 18. Indications  Large Restorations  Better strength  Control of contours and contacts  Better alternative to a crown to teeth that have been greatly weakened by caries or by a large failing restoration, but facial and lingual surfaces are relatively unaffected by the disease/injury.  For such a weakened teeth, the superior physical properties of the casting alloys are desirable to withstand occlusal loads placed on the restorations.
  19. 19.  An onlay can be designed to distribute occlusal loads over the tooth in such a manner that decreases the chances of fracture of the tooth in the future.  Maintaining facial and lingual enamel/cementum is conducive to maintaining the health of contiguous soft tissue.
  20. 20.  Endodontically treated teeth  Molars and Premolars with endodontic treatment can be restored with a cast metal onlay  Teeth at risk for fracture  Teeth with extensive restorations, Fracture lines in enamel and dentin must be recognised as cleavage planes for future tooth fracture.
  21. 21.  Dental rehabilitation with cast metal alloys  When cast metal restorations have already been used to restore adjacent or opposite teeth, the continued use of the same metal to avoid electrical or corrosive activity that may occur if the dissimilar metals are used.  Diastema Closure and Occlusal plane correction  Indicated when extension of mesiodistal dimension of tooth is necessary.  Cast onlays may also be used to correct the occlusal plane of a slightly tilted tooth.
  22. 22.  Removable Prosthodontic Abutment  Teeth that are to serve as abutments for a removable partial denture can be restored with a cast metal restoration.  Advantages: 1. Superior physical properties allow it to withstand the forces imparted by the partial denture. 2. The rest seats, guiding planes and other aspects of contour relating to the RPD are better controlled when the indirect technique is used.
  23. 23. Contraindications  High Caries rate  Facial and Lingual tooth surface must be free of caries or previous restorations.  If present, the tooth must be restored with a Full crown.  Young patients  Amalgam or Composites are the restorative material of choice for Class I and II restorations unless the tooth is severely broken down or endodontically restored.
  24. 24.  Esthetics  Their use is restricted to the tooth surfaces that are not visible at conversational distance.  Small restorations  Amalgam and Composites serve as a better option.
  25. 25. Advantages  Strength  Biocompatibility  Low wear  Control of Contours and Contacts
  26. 26. Disadvantages  Number of Appointments and More Chair time  Provisionalisation is required  Costs  Technique sensitive  Splitting forces
  27. 27. Preoperative Considerations  Occlusion  Occlusal contacts must be evalauted  It must be decided if existing occlusal relationships can be improved with a cast metal restoration  Evaluation at Maximum Intercuspation, and also during eccentric movements  The pattern of occlusal contacts influences the preparation design, the selection of interocclusal records, and the type of articulator.
  28. 28.  Anaesthesia  Eliminates pain, Reduces Salivation  Considerations forTemporary restorations  An index can be fabricated preoperatively using elastomeric impression material or alginate.
  29. 29. Tooth Preparations for Cast Metal Restorations
  30. 30. Principles of Cavity Preparation  For inlay work the dual objectives in cavity preparation are to remove the caries and shape the cavity for an effective restoration. Factors governing a good inlay preparation:  Caries:  The final outline of the cavity depends on the extent of the carious lesion.  Where it is minimal an initial penetration is made just into dentine and the cavity is extended at this optimal depth to the classic outline.
  31. 31.  The outline is decided by the class of the cavity and the need to remove adjacent stagnation areas on the tooth surface.  A larger carious lesion will have caused some obvious cavitation due to enamel breakdown.The first stage here is to remove undermined enamel in order to obtain access to the lesion. Carious enamel at the DE junction is removed next. Further undermined enamel is removed next and any remaining fissures are included in the cavity outline.
  32. 32.  Retention and Resistance:  Resistance to occlusal stresses is generally obtained by providing flat pulpal and gingival floors of the cavity, if necessary by the addition of a cement base over the pulp.  Resistance to lateral stresses is provided by an occlusal lock and by axial walls.  For good retention, an inlay must have a single path of insertion into its cavity in a direction which is usually in line with the main occlusal load, masticatory forces will then tend to seat the inlay more securely into its cavity.
  33. 33.  This single path of insertion is achieved by near parellelism of the cavity walls so that the inlay can be displaced only along the path of its insertion. The friction provided between the near parallel walls and the inlay when its cemented will prevent this displacement.  Cavo-surface Angles  The marginal integrity of an inlay depends on the existence of a well defined cavo surface angle. They are usual cut in enamel and must be smooth and finished with great care, crumbling of the margin due to minor irregularities may cause recurrent caries.
  34. 34.  The margin must also allow for burnishing of the margins of the restoration if a gold restoration is being planned.  Minimum Cavo surface angle which permits thin enough gold capable of being burnished is about 135°.  This special preparation is known as bevelling. They usually extend half the thickness in enamel except cervically where the enamel is thinner and a full thickness of enamel is bevelled.
  35. 35. Class I Cavity  Inlays for this type of cavity have a very limited application, but may be considered where opposing cast restorations are already present or are being planned.  Generally inlays are not indicated for Class I cavities, Amalgam or composites provide excellent restorative option.  A very large Class I cavity requiring cuspal coverage may be restored with an inlay if the operator is satisfied that the caries activity is low enough.
  36. 36. Cavity Preparation  Step 1: Access: the tooth is penetrated to just within the dentine, using aTC bur  Step 2: Extension:The fissures are removed by extending at the optimum depth, using a tapered fissure bur.This instrument if used correctly, produces the correct taper with a flat floor.  Step 3: Caries Removal and Lining: Remaining caries is excavated and the resulting cavity lined to produce a flat floor just within dentine.
  37. 37.  Step 4: Finishing: Sharp burs running at low speed is recommended for the intracoronal details and Bladeless or 40 bladedTC burs used at ultra high speed are recommended for the cavo- surface angles.  Bevelling is not necessary when the cavo surface angle is greater than 135°. But when the angle is less than 135° the margin must be bevelled.
  38. 38.  A direct wax pattern is usually indicated for this type of a cavity.  Type II wax (Hard type) is used.
  39. 39. Class II Cavity  Proximal restorations are by far the most common restorations in Restorative dentistry.  A Class II restoration may vary from a relatively conservative MO/DO Box preparation to Mesio-occluso-Distal Restorations to Cusp capping.
  40. 40. Box Preparation  This type of a preparation consists of an occlusal part in dovetail form and an proximal box. The Steps in preparation are:  Step 1: Access:A smallTC bur is used to cut just within the marginal ridge and to penetrate along the enamel-dentine junction to the proximal caries.  Step 2: Extension of the Proximal box: The proximal cut is extended to gingival level with a fine, tapered fissure bur at ultra speed. Sweeping cuts are made bucco-lingually to outline the lateral extent. Undermined enamel is removed using a chisel or a hatchet.
  41. 41. Tapered fissure bur is then used to remove irregularities on the proximal box and flatten the gingival floor.  Step 3: Outline of the occlusal form:Tapered fissure bur is used to outline the occlusal part of the preparation.The occlusal outline is similar to that of a Class I cavity.
  42. 42.  Step 4: Finishing the Proximal Box:The Proximal box is completed using a fine abrasive disc or a chisel to plane its vertical walls and to sharpen its line angles. To achieve optimum cavo- surface margin, the buccal and lingual walls may be flared using fine abrasive discs. Gingival enamel is finished using aTC finishing bur.
  43. 43.  Step 5: Gingival Lock: a groove may be cut into the dentine of the gingival floor using a reverse GMT. This acts as a stop. But this feature is not essential.  Step 6: Finishing the Occlusal Dovetail:The cut enamel surface of the dovetail is smoothened with a plain cut bur.  Step 7: Caries Removal and Lining: Any caries remaining is removed and base is applied, deep excavations need a protective sub-base.
  44. 44. Extensive Proximal Cavities  In case of extensive Proximal cavities, the approach to cavity preparation is slightly modified,  Here, the undermined enamel and marginal ridge are removed first using a chisel, followed by initial minimal extension of the proximal and occlusal parts of the cavity followed by the removal of all the caries and final extension.
  45. 45. MOD cavities  This type of cavity with its combined mesial and distal parts is more difficult to prepare because of the extra surfaces which must be kept to a common path of withdrawal.  In case of an unaffected, strong oblique ridge, a separate MO and DO cavities are prepared and restored.  The distoocclusolingual restoration that caps the distolingual cusp is preferable to the DO restoration because it protects the miniature distolingual cusp from subsequent fracture.
  46. 46. Modification for Esthetics  For esthetic reasons, minimum flare is desired for the mesiofacial proximal wall in the maxillary premolars and first molars in class II cast metal preparations.  The mesiofacial margin is minimally extended facially of contact to such a position that the margin is barely visible from a facial viewing position.  To accomplish this, the secondary flare is omitted, and the wall and margin are developed with a chisel or enamel hatchet and final smoothing with a fine-grit paper disc, or a narrow diamond or bur when access permits.
  47. 47. For abutment teeth  Extending the facial, lingual, and gingival margins may be indicated on the proximal surfaces of abutments for RPDs to increase the surface area for development of guiding planes.  In addition, the occlusal outline form must be wide enough faciolingually to accommodate any contemplated rest preparations without involving the margins of the restoration. These extensions may be accomplished by simply increasing the width of the bevels
  48. 48. Extension gingivally to include root-surface lesions  The gingival extension should be accomplished primarily by lengthening the gingival bevel, especially when preparing a tooth that has a longer clinical crown than normal as a result of gingival recession.  It is necessary to only slightly extend the gingival floor, and although the axial wall consequently must be moved pulpally, this should be minimal.  Extending the preparation gingivally without these modifications would result in a dangerous encroachment of the axial wall on the pulp
  49. 49. Capping cusps  The facial and lingual margins on the occlusal surface frequently must be extended toward the cusp tips to the extent of existing restorative materials and to uncover caries.  Undermined occlusal enamel should be removed because it is weak. Moreover, removing such enamel provides access for proper excavation of caries.
  50. 50.  When the occlusal outline is extended up the cusp slopes more than half the distance from any primary occlusal groove (central, facial, or lingual) to the cusp tip, capping the cusp should be considered.  If the preparation outline is extended two thirds of this distance or more, capping the cusp protects the weak, underlying cuspal structure from fracture due to the masticatory forces and also removes the occlusal margin from a region subjected to heavy stress and wear.
  51. 51.  Cusp reduction appreciably decreases retention form because of decreasing the height of the vertical walls; consequently, proximal retention grooves usually are recommended.  It may be necessary to increase retention form by extending facial and lingual groove regions of the respective surfaces, or by collar and skirt.  These additional retention features also provide the desired resistance form against forces tending to split the tooth.
  52. 52.  A full crown is indicated if both the lingual and facial smooth surfaces are defective, especially if the tooth is a second or third molar.  When only a portion of the facial smooth surface is carious and the lingual surfaces of the teeth are conspicuously free of caries, an MOD inlay or onlay with a lingual groove extension is chosen over the crown because the former is more favorable to the health of the gingival tissues and more conservative in the removal of tooth structure.
  53. 53.  If distofacial defect is more extensive and deeper into the tooth a gingival shoulder extending from the distal gingival floor around to include the affected facial surface is recommended.This shoulder partially provides the desired resistance form.
  54. 54. Class III Cavities  Inlays for simple Class III cavities are not generally recommended although exceptionally one with a small palatal extension may be suitable for a denture rest.  An important indication for a class III inlay is the distopalatal restoration used as a minor retainer in an upper canine or central incisor for a fixed- movable bridge. Unfortunately, this design decreases the retention of the inlay and additional retention is usually necessary.This is obtained by using pin placed within the palatal dovetail at the farthest point from the proximal box.
  55. 55. Tooth Preparation  The lingual outline is formed using aTC Bur.  Lingual dovetail or lock is used to give resistance form.  It should be 1 mm deep.
  56. 56.  Continue the cut along the midline of the cingulum to 1 mm of the gingiva. Second cut should extend distally close to the lesion being restored on the distal aspect.  A reverse L shape outline is formed.  Proximal box is prepared without preparing the facial enamel, to avoid unesthetic display of metal, and also to conserve tooth structure.
  57. 57.  Smoothen the axial wall of the box.  Proximal flares and bevels are given using a flame shaped diamond bur.  The entire finish line must then be finished using a flameTC finishing bur.
  58. 58. Class V Cavities  There are 2 distinct lesions at the cervical margin of the buccal or lingual surfcare of a tooth which may need restorations. One begins as caries of the enamel at the gingival third of the crown and the other is a cavity of cementum and dentin at the cervical margin of a tooth with gingival recession and is due to abrasion forming a cavity with an overhang of sound enamel.  With the advent of restorative materials like GIC, inlays are not a choice of treatment for most of these patients.
  59. 59. Tooth Preparation  Outline is made using aTC bus  The preparation should be 1 mm deep axially. If there is an extensive lesion then create a ledge around the periphery of the preparation extensions.  Extend the preparation to the line angle of the tooth. Keep the finish line supragingival.
  60. 60.  The occlusal finish line should extend no farther than the height of contour.  Pinholes are drilled using a 0.6mm drill.  At the mesial and distal edges of the outline form.
  61. 61.  Bevel is given using the flame diamond bur  Place 45 degree bevel around the periphery of the entire outline form, approximately 0.5mm in width.  Finish the preparation with a plane carbide finishing bur.
  62. 62. Onlay Preparation  The cast metal onlay restoration spans the gap between the inlay, which is primarily an intracoronal restoration, and the full crown, which is a totally extracoronal restoration. The cast metal onlay by definition caps all of the cusps of a posterior tooth and can be designed to help strengthen a tooth that has been weakened by caries or previous restorative experiences.  It can be designed to distribute occlusal loads over the tooth in a manner that greatly decreases the chance of future fracture. It is more conservative of tooth structure than the full crown preparation and its supragingival margins, when possible, are less irritating to the gingiva.
  63. 63.  Usually an onlay diagnosis is made preoperatively because of the tooth's status. However, sometimes the diagnosis is deferred until extension of the occlusal step of an inlay preparation facially and lingually to the limits of the carious lesion demonstrates that cusp reduction is mandatory.
  64. 64. Occlusal Considerations  Clinicians have linked marginal failures to weakened cusps and preparation walls bending away from the restoration under stress  Isthmus width and depth have also been recognised as contributing factors  As long as the tooth is intact it has structural integrity, when a tooth preparation is done tooth is weakened and is prone to fracture.  Premolar-11-52% less fracture resistance when class I isthmus is cut into oclusal surface  17-57% less strength when it has proximo- occlusal preparation
  65. 65.  Only 36-61% of its strength left when MOD preparation is done so chances of fracture at the isthmus is more
  66. 66.  Cusp have a mechanical height that is equal to the anatomical height measured from the cusp tip to the level of central groove  In MOD mechanical length is greatly increased –distance from cusp tip to gingival extension of Preparation. This causes elongation of lever arm and hence in small tooth can cause fracture
  67. 67. • Inlay has a tendency to wedge the cusps apart particularly when there is a wide isthmus. • Occlusal forces applied produces stress along the side of the restoration and at its base
  68. 68.  This situation in could lead to fracture of the tooth  Onlay will distribute the forces evenly over a wide area reducing the potential for breakage  The wedging effect produced by inlays were shown by photoelastic stress analysis by Fisher et al.Inlay produced stress concentration at the walls of the isthmus and the line angles
  69. 69. Tooth Preparation Initial Preparation  Occlusal reduction: tapered fissure carbide and round-end diamond bur used
  70. 70.  1.5 mm clearance on functional cusps  1.0 mm clearance for nonfunctional cusp  Reduction should follow the general topography of the occlusal surface.
  71. 71.  Functional Cusp Bevel is given
  72. 72.  Occlusal Shoulder on the functional cusp side  Provides for greater bulk of metal on functional cusp  Increased resistance  Reinforced margin (more durable)
  73. 73.  Occlusal isthmus preparation  Flat end tapered fissure carbide bur used.  Isthmus is made now if not prepared earlier while removing the existing restoration.  Bur held parallel to long axis of the tooth.
  74. 74.  Prepare pulpal floor along the central groove extend mesially and distally, facially and lingually • Should be 1.0mm shallower than the isthmus in an inlay because occlusal surface has been reduced already
  75. 75. • Isthmus should be ½ to 1/3rd the width between the facial and lingual cusp tips. • 2-5 degree taper per wall- (according to Sturdevant)  When the wall length or surface involvement increases, taper increased.  Taper reduced- when wall is short and need for retention is more narrow at pulpal surface
  76. 76.  Proximal box preparation  Tapered fissure carbide bur. Mesial and distal proximal boxes are prepared to the level of the gingival crest  Gingival floor should be 1mm wide and the Proximal clearance should be 0.5mm
  77. 77.  Buccal and Lingual walls should diverge occlusally  Use hatchets/chisels to plane the facial and lingual walls and refine the axiobuccal and axiolingual line angles  Shallow (0.3mm) retention grooves cut in facioaxial & linguoaxial line angles with a carbide bur in dentine for retention
  78. 78. Final preparation  Removal of infected carious dentin and defective restorative materials and pulp protection  If the proximal boxes and the occlusal step has been extended properly then any remaining caries or restorative material should be visible. It should be removed.  All the horizontal surfaces i.e., the pulpal floor, gingival floor and shoulder should be smoothened using an endcutting bur.
  79. 79. Smoothening of Isthmus, gingival seat and Shoulder
  80. 80. Proximal Flares  Primary flare and Secondary flare Primary flare  part of circumferential tie  similar to a long bevel  formed of enamel and part of dentin  Placed on facial and lingual proximal wall.  have 45o angulation to inner dentinal wall proper  places proximal margins in cleansable finishable areas.
  81. 81. Secondary Flare  Is a flat plane superimposed on a primary flare usually prepared solely in enamel but may involve dentin also  Places margins in more cleansable finishable areas  Results in 40 degrees marginal metal.  A more blunted and stronger enamel margin is produced  May have different angulations, involvement & extent
  82. 82. Indications of Secondary Flare  Broad contact areas, secondary flare brings the facial and lingual margins to finishable, cleansable areas, without sacrificing much tooth structure.  In case caries is widely extended in buccolingual dimension.  To include surface defects on facial and lingual aspect beyond the primary flare.  To overcome undercuts that may be present at the cervical aspect of the facial and lingual proximal walls
  83. 83.  Flame shaped diamond used  Place the flares on the proximal box from within starting with the tip of the flame diamond  A wide enamel hatchet can also be used to form the flares
  84. 84. Finishing bevels  Gingival bevel  Flame diamond bur used  0.5mm to 1mm wide  Placed along the entire gingival floor of the box  Should blend with the flares without forming an undercut.
  85. 85.  Should blend with the flares without forming an undercut.  Removes unsupported enamel  Results in 30 degree marginal metal that is easily burnishable.  A lap sliding fit is produced at the gingival margin
  86. 86. Facial and lingual bevels  Flame diamond used  0.5mm wide  Placed on buccal (maxillary)and lingual (mandibular) occlusal surfaces, should be blended into the flares.  Bevel should result in 40 degrees marginal metal  An Occlusal shoulder bevel is also placed
  87. 87. Additional Retentive features  Skirt Preparation  Collar Preparation  Slot Preparation
  88. 88. Skirt Preparation  When the proximal portion of a class II cavity for an onlay is being prepared and the lingual wall is partially or totally absent the retention is provided by skirt preparation of the facial margin and vice versa  Recommended when proximal contours and contacts are to be extended more than the normal dimensions  When splinting posterior teeth together with onlay.The additional retension and resistance is very useful because of the stress on each un
  89. 89. Collar Preparation  To increase the retention and resistance form when preparing a weakened tooth for a MOD onlay capping all the cusps , a facial or lingual collar or both may be provided  To reduce the display of metal on the facial surfaces of the maxillary premolars and the first molars are usually not prepared for collar.
  90. 90. Slot Preparation  After cusp reduction the vertical walls of the occlusal step portion of the preparation are reduced so they provide very little retention form. In such cases necessary retention can be obtained by making a slot preparation  It is indicated in short clinical crown and in cusps that have been reduced  A slot removes more tooth structure than for a pin but it is less likely to cause microfractures in dentin
  91. 91. Restorative techniques  Interocclusal records: If the patient has sufficient canine guidance to provide disocclusion of the posterior teeth, then the necessary registration of the opposing teeth can be obtained by (1) making a MI interocclusal record with commercially available bite registration pastes or (2) making full-arch impressions and mounting the casts made from these impressions on a simple hinge articulator.
  92. 92.  But, Cast metal restorations made with these simple bite registration techniques often require adjustments in the mouth to alleviate interferences during mandibular movements.  The use of full-arch casts mounted on a semiadjustable articulator is recommended when restoring a large portion of the patient's posterior occlusion with cast metal restorations.  It involves very little extra chair time and gives the laboratory technician much more information about the general occlusal scheme, pathways of cusps, opposing cusp steepness and groove direction, and the anatomy of the other teeth in the mouth.
  93. 93. Temporary Restoration  Direct technique  Indirect technique
  94. 94. Final Impression  The indirect technique for making cast metal restorations is accurate and dependable.  Fabrication of the cast metal restoration takes place in the laboratory, on a cast made from an impression of the prepared and adjacent unprepared teeth.
  95. 95.  Ideal Requirements of an impression material:  It must become elastic after placement in the mouth because it must be withdrawn from undercut regions that usually exist on the prepared and adjacent teeth.  It must have adequate strength to resist breaking or tearing on removal from the mouth.  It must have adequate dimensional accuracy, stability, and reproduction of detail so that it is an exact negative imprint of the prepared and adjacent unprepared teeth.  It must have handling and setting characteristics that meet clinical requirements.  It must be free of toxic or irritating components.  It must be able to be disinfected without distortion.
  96. 96.  The most common impression material of choice for indirect restorations are the polyvinyl siloxanes.  Tissue retraction is recommended in case of subgingival margins. Use of appropriate styptics are recommended in case of hemorrhage.
  97. 97. Wax Patterns  The Impression are poured and working cast and Dies are prepared.  The working casts/Dies are mounted using the interocclusal record made previously.  The Patterns are formed using type I Inlay pattern wax.The proximal contours and contact are established first.  Then the occlusal wax up is done. Payne has advocated that the facioligual width of the tooth be divided in quarters and then waxed up.  Spruing, investing and Casting are done in the conventional manner.
  98. 98. Seating, adjusting & Polishing the casting  Fit of the casting is confirmed on the die.  The margins are burnished using a ball or a Beavertail burnisher in case of gold restorations.  The occlusion is checked using articulating paper and corrections are made if any by selective grinding.  Rubber discs and points are used to polish the casting, followed by a soft bristle wheel disc and tripoli.
  99. 99.  In the patient’s mouth, the prepared tooth is isolated.  Check the proximal contacts. Passing a floss interproximally will indicate the tightness and position of the contact.  If contact is open then soldering at the contact point must be done.  Occlusion is checked in both MI and Eccentric movements and correction made if any.  Margins are adpated in case of gold alloys using a burnisher.
  100. 100. Cementation  Before Cementation, isolate the tooth from saliva with the aid of cotton rolls, and saliva ejector if needed.  Use a air syringe to dry the preparation walls, but do not desiccate them.  Manipulate the cement of choice according to manufacturers instructions.  The casting is cemented, by coating the preparation surface of the casting with the cement and place the casting in place using operative pliers.Then press using ball burnisher in the pit areas.Then, ask the patient to bite on a burlew disc. Remove the excess cement, check for excess cement interproximally using a floss.
  101. 101. Repair  In case of fracture of the cast restoration, if the area is small and if the restoration is intact and retentive, then it may be repaired using composites or amalgam.
  103. 103. Contents  Introduction  Definitions  Cast Metal Restorations  Indications and Contraindications  Advantages and Disadvantages  Tooth Preparation  Restoration  Onlays
  104. 104.  Tooth-Coloured Restorations  Indirect Composites  Ceramic Restorations  Indications and Contraindications  Advantages and Disadvantages  Tooth Preparation  Restoration  Repair of Restorations  CAD-CAM based restorations  Inlay retained Bridges  Strength and Longevity of Inlays and Onlays  Review of Literature
  105. 105. Mondelli JPD 1980  All occlusal cavity preparations decrease the strength of teeth in proportion to the width of the preparation.  The Class I occlusal preparation reduces the strength of the tooth less than the occlusal portion of the Class II preparation with equal width.  The width of the isthmus was a statistically significant factor. A desirable width of the isthmus is one-fourth the intercuspal distance. This dimension provides greater strength regardless of the Class of the cavity.
  106. 106. Spruing for Inlays and Onlays  Patterns for inlays and onlays maybe sprued in either of the following ways:  Sprue former positioned at the contact point, this preserves occlusal anatomy and will result in increased expansion in the mesiodistal direction due to mold expansion out end of the casting ring.  Sprue former placed at the marginal ridges, this preserves contacts at the expense of some occlusal anatomy and provides for equal ex[ansion in all directions.
  107. 107. Direct wax/Indirect wax According to Anusavice,  Type I – MediumWax used in DirectTechniques  Type II – Soft waxes used in Indirect technique  Composition: NaturalWaxes(Hydrocarbons of paraffin and microcrystalline wax series, carnauba wax, candelila wax and resins) and /or synthetic waxes.They contain compatible fillers to control expansion and shrinkage of the wax product. ANSI/ADA Speci fication No. 4
  108. 108. Inlay Wax flow(%) Type of wax T=30° C (Max) T=37° C (Max) T=40° C (Min) T=40° C (Max) T=45° C (Min) T=45° C (Max) I - 1.0 - 20 70 90 II 1.0 - 50 - 70 90 Philips’ Science of Dental Materials, Anusavice, Eleventh Edition
  109. 109. According to Craig,  Type 1 (soft) – used as an indirect technique wax  Type 2(hard) – used for direct patterns in the mouth Craigs’ Resorative Dental Materials, Powers and Sakaguchi, twelfth edition
  110. 110. Provisionalisation  Polymethyl methacrylate(Duralay)  Polyethyl methacrylate(Snap)  Polyvinyl methacrylate(Trim)  Protemp II : Bis-acryl composite resin  VLC urethane dimethacrylate(Triad)
  111. 111. Margins of a class V cavity in case of a gingival recession?
  112. 112. Tooth Coloured Inlays and Onlays
  113. 113.  Tooth-coloured indirect systems include laboratory-processed composites or ceramics such as porcelain fired on refractory dies or hot pressed glasses.  In addition, chairside computer-aided design/computer-assisted manufacturing (CAD/CAM) systems are currently available and are used to fabricate ceramic restorations.
  114. 114. Indications  The indications for Classes I or II indirect tooth-coloured restorations relate to a combination of esthetic demands and size of the restoration and include the following:  Esthetics: Indirect tooth-coloured restorations are indicated for Class I or Class II restorations located in areas of esthetic importance for the patient.
  115. 115.  Large defects or previous restorations: Indirect tooth-coloured restorations should be considered for restoration of large Class I or Class II defects or replacement of large existing compromised restorations, especially those that are wide faciolingually and require cusp coverage. Large preparations are best restored with adhesive restorations that strengthen the remaining tooth structure.  Indirect tooth-coloured restorative materials are more durable than direct composites, especially in regard to maintaining occlusal surfaces and occlusal contacts .
  116. 116.  The wear resistance provided by indirect materials is especially important in large posterior restorations that involve most or all of the occlusal contacts.  However, without sufficient bulk, an extensive indirect ceramic or composite restoration may fracture under occlusal loading, particularly in the molar region  Economic factors: Some patients desire the best dental treatment available, regardless of cost. For these patients, indirect tooth-coloured restorations may be indicated not only for large restorations, but also for moderate-sized restorations that might otherwise be restored with a direct restorative material.
  117. 117. Contraindications  Heavy occlusal forces: Ceramic restorations may fracture when they lack sufficient bulk or are subject to excessive occlusal stress, as in patients who have bruxing or clenching habits.  Inability to maintain a dry field: Adhesive techniques require near-perfect moisture control to ensure successful long-term clinical results.
  118. 118.  Deep subgingival preparations: Although this is not an absolute contraindication, preparations with deep subgingival margins should be avoided.These margins are difficult to record with an impression and are difficult to finish. Additionally, bonding to enamel margins is greatly preferred, especially along gingival margins of proximal boxes.
  119. 119. Advantages  Esthetics  Conservative of tooth structure removal (less extension)  Insulative, having low thermal conductivity  Repairable
  120. 120.  Improved physical properties: A wide variety of high strength tooth-coloured restorative materials, including laboratory-processed and computer- milled composites and ceramics, can be used with indirect techniques.  Indirect restorations have better physical properties than direct composite restorations because they are fabricated under relatively ideal laboratory conditions.  Also, while CAD/CAM restorations are generally fabricated chairside, the materials themselves are manufactured under very nearly ideal industrial conditions .
  121. 121.  Wear resistance: Ceramic restorations are more wear resistant than direct composite restorations, an especially critical factor when restoring large occlusal areas of posterior teeth. Laboratory-processed composite restorations wear more than ceramics, but less than direct composites.
  122. 122.  Reduced polymerization shrinkage: With indirect techniques, the bulk of the preparation is filled with the indirect tooth- coloured restoration, and stresses are reduced because very little composite cement is used during cementation. Although shrinkage of composite in thin bonded layers can produce relatively high stress, studies indicate that indirect composite restorations have fewer marginal voids, less microleakage, and less postoperative sensitivity than direct composites.
  123. 123.  Ability to strengthen remaining tooth structure:Tooth structure weakened by caries, trauma, and/or preparation can be strengthened by adhesively bonding indirect inlays and onlays.The reduced polymerization shrinkage stress obtained with the indirect technique is also desirable when restoring such weakened teeth.
  124. 124.  More precise control of contours and contacts: Indirect techniques usually provide better contours (especially proximal contours direct restorations because of the improved access and visibility ) and occlusal contacts than direct restorations.  Biocompatibility and good tissue response:Ceramic materials are considered the most chemically inert of all materials.They are biocompatible and generally are associated with a good soft tissue response.The pulpal biocompatibility of the indirect techniques is related more to the adhesive composite cements rather than the ceramic materials used.
  125. 125.  Increased auxiliary support: Most indirect techniques allow the fabrication of the restoration to be totally or partially delegated to dental laboratory technicians. Such delegation allows for more efficient use of the dentist's time.
  126. 126. Disadvantages  Increased cost and time: Most indirect techniques require two patient appointments, plus fabrication of a temporary restoration.These factors, along with laboratory fees, contribute to the greater cost of indirect restorations as compared to direct restorations.  However, while indirect tooth-coloured inlays and onlays are more expensive than direct restorations (amalgams or composites), they are usually less costly than more invasive esthetic alternatives, such as all-ceramic or porcelain-fused-to-metal (PFM) crowns.
  127. 127.  Technique sensitivity: Restorations made using indirect techniques require a high level of operator skill. Precision is necessary during preparation, impression, try-in, cementation, and finishing the restoration.  Brittleness of ceramics: A ceramic restoration can fracture if the preparation does not provide adequate thickness to resist occlusal forces or if the restoration is not appropriately supported by the cement medium and the preparation. Fractures can occur either during try-in or after cementation, especially in patients who generate unusually high occlusal forces.
  128. 128.  Wear of opposing dentition and restorations: Ceramic materials can cause excessive wear of opposing enamel and/or restorations. Recent improvements in ceramics have reduced this problem, but ceramics, particularly if rough and unpolished, can wear opposing teeth and restorations.
  129. 129.  Resin-to-resin bonding difficulties: Laboratory- processed composites are highly cross-linked, so few double bonds remain available for chemical adhesion of the composite cement . Therefore the composite restoration must be mechanically abraded and/or chemically treated to facilitate adhesion of the cement . The bond between the indirect composite restoration and the composite cement is the weak link in the system. However, bonding of composite cements to properly treated ceramic restorations is not a problem.
  130. 130.  Short clinical track record: Indirect bonded tooth coloured restorations have become relatively popular only in recent years and are still not placed by many practitioners. Fewer controlled clinical trials are available, so the long-term durability of these restorations, although expected to be good, is not particularly well documented .
  131. 131.  Low potential for repair: Indirect restorations, particularly ceramic inlays/onlays, are difficult to repair in the event of a partial fracture. If the fracture occurs in the restoration, an indirect composite inlay or onlay can be repaired using an adhesive system and a lightcured restorative composite.The bond strengths of indirect composite repair and direct composite repair appear to be equivalent .
  132. 132.  When a partial fracture occurs in a ceramic inlay/onlay, repair is usually not a definitive treatment.The actual procedure (mechanical roughening, etching with hydrofluoric acid, and application of a silane coupling agent before restoring with an adhesive and composite) is relatively simple.  However, because ceramic inlays/onlays are indicated in areas where occlusal wear, esthetics, and resistance are important, direct composite repairs are not suitable because that composite will be exposed to a challenging environment.
  133. 133.  Difficult intraoral polishing: Indirect composite restorations can be polished intraorally with the same instruments/ materials used to polish direct composites.  Ceramics, on the other hand, are more difficult to polish after they have been cemented because of either limited access or lack of appropriate instrumentation.
  135. 135.  The physical properties of composite restorations are improved when the composite is free of voids, and the resin matrix is maximally polymerized.  Well-cured restorations is best accomplished in the laboratory using devices that polymerize the composite under pressure, vacuum, inert gas, intense light, heat, or a combination of these conditions. Several commercial systems use these techniques to optimize the physical properties of their composite materials.
  136. 136.  Laboratory-processed composite inlays and onlays are more resistant to occlusal wear than direct composites, particularly in occlusal contact areas. However, they are less wear-resistant than ceramic restorations.  They offer easy adjustment, low wear of the opposing dentition, good esthetics, and potential for repair.
  137. 137. Indications for Indirect composite inlays and onlays  When maximum wear resistance is desired from a composite restoration,  When achievement of proper contours and contacts would otherwise be difficult, and  When a ceramic restoration is not indicated because of cost or concerns about wear of the opposing dentition.
  138. 138.  A study by Donly et al, on a comparison of composite inlays/onlays and cast gold inlay/onlays revealed no statistically significant differences. However, composite inlays showed a 50% failure rate in molars suggesting that they were better suited for restoration of premolars.
  139. 139. Steps in Fabrication  The indirect composite restoration is initially formed on a replica of the prepared tooth.  The composite is built up in layers, polymerizing each layer with a brief exposure to a visible lightcuring unit.  After it is built to full contour, the restoration is coated with a special gel to block out air and thus prevent formation of an oxygen-inhibited surface layer.  Final curing is accomplished by inserting the inlay into an ovenlike device that exposes the composite to additional light and heat.  The cured composite inlay is trimmed, finished, and polished in the laboratory.
  140. 140. Materials used  Tetric (IvoclarVivadent)  Z100 (3M ESPE) (85%wt ultrafine Zirconia-Silica Ceramic particles that reinforce a highly crosslinked polymeric matrix)  Maxxim  Gradia GC (hybrid MFR formulation, couples a microfine ceramic/prepolymer filler with a urethane dimethacrylate matrix to produce a superior ceramic composite with exceptionally high strength and superior polishability.
  142. 142.  The ceramic materials used are feldspathic porcelain, hot pressed ceramics, and machinable ceramics designed for use with CAD/CAM systems.  The physical and mechanical properties of ceramics come closer to matching those of enamel than do composites.  They have excellent wear resistance and a coefficient of thermal expansion very close to that of tooth structure.
  143. 143. Feldspathic Porcelain Inlays and Onlays  Dental porcelains are partially crystalline minerals (feldspar, silica, alumina) dispersed in a glass matrix. Porcelain restorations are made from finely ground ceramic powders that are mixed with distilled water or a special liquid, shaped into the desired form, then fired and fused together to form a translucent, material that looks like tooth structure.  Currently, many ceramic inlays and onlays are fabricated in the dental laboratory by firing dental porcelains on refractory dies.
  144. 144.  Many dental laboratories use this technique to fabricate ceramic inlays and onlays because of its low startup cost.  The ceramic powders and investments are relatively inexpensive, and the technique is compatible with most existing ceramic laboratory equipment such as firing furnaces.  The major disadvantage of this technique is its technique sensitivity. Problems with fit and strength may be present. Inlays and onlays fabricated with this technique must be handled very gently during tryin to avoid fracture.  Even after cementation, the incidence of fracture is rather high for this type of ceramic restorations.
  145. 145. Hot Pressed Glass Ceramics  In 1968, it was discovered that certain glasses could be modified with nucleating agents and, upon heat treatment, be changed into ceramics with organized crystalline forms.  Such glassceramics were stronger, had a higher melting point than noncrystalline glass, and had variable coefficients of thermal expansion.
  146. 146.  At first, these glass-ceramics were primarily developed for cookware and other heatresistant products. In 1984, the glass- ceramic material Dicor (Dentsply International,York, Pennsylvania) was patented and rapidly became a popular ceramic for dental restorations.  A major disadvantage of Dicor was its translucency, which necessitated external application of all shading.
  147. 147.  Dicor restorations were made using a lost-wax, centrifugal casting process. Newer leucite- reinforced glassceramic systems also use the lost-wax method, but the material is heated to a high temperature and pneumatically pressed, rather than centrifuged, into a mold.  Although studies by Catell et al indicate that hot pressed ceramics are not significantly stronger than fired feldspathic porcelains.They do appear to provide better clinical service.
  148. 148.  The Moulds for pressed ceramics are fabricated using the lost wax technique, and the ceramic ingots are pressed into the mold at 1100°C.  The advantages of hot pressed ceramics are their (1) similarity to traditional "wax-up" processes, (2) excellent marginal fit, and (3) relatively high strength.
  149. 149.  The surface hardness and occlusal wear of these ceramics are very similar to enamel. Pressed ceramic inlays are stronger than porcelain inlays made on refractory dies, but are still quite fragile until cemented.  The incidence of postcementation fracture for pressed ceramic inlays is expected to be lower than that for ceramic inlays fired on refractory dies, but higher than for inlays made with CAD/CAM systems.
  150. 150. CAD CAM  Rapid improvements in technology have spawned several computerized devices that can fabricate ceramic inlays and onlays from high-quality ceramics in a matter of minutes.  Some CAD/CAM systems are very expensive laboratory-based units requiring the submission of an impression or working cast of the prepared tooth.  The CEREC system was the first commercially available CAD/CAM system developed for the rapid chairside design and fabrication of ceramic restorations.The recent version of this device is the CEREC 3 (Sirona USA, Charlotte, North Carolina).
  151. 151.  Generation of a CEREC restoration begins after the dentist prepares the tooth and uses a scanning device to collect information about the shape of the preparation and its relationship with the surrounding structures. This step is termed an optical impression.
  152. 152.  A video image of the prepared tooth is displayed to ensure proper positioning of the scanning device.The CEREC systems use the optical techniques of Moire fringe displacement and active triangulation to measure the height and depth of the preparation.
  153. 153.  The system projects an image of the preparation and surrounding structures on a monitor, allowing the dentist or auxiliary personnel to use the CAD portion of the system to design the restoration.  The operator must input and/or confirm some of the boundaries of the restoration, such as the position of the gingival margins. Once the restoration has been designed, the computer directs a micromilling device (CAM portion of the system), which mills the restoration out of a block of high quality ceramic or composite in a matter of minutes.The restoration is removed from the milling device, ready for try-in and cementation.
  154. 154.  The CEREC systems are designed to be used chairside, which eliminates the need for a conventional impression, temporary restoration, and multiple appointments. In addition to the speed of these systems, a major advantage is the quality of the restorative material.  Manufacturers make blocks of machinable ceramics or machinable composites specifically for computer-assisted milling devices. Because these materials are fabricated under ideal industrial conditions, their physical properties have been optimized.
  155. 155.  The major disadvantages of CAD/CAM systems are high initial cost and the need for extra training.  However, CAD/CAM technology is changing rapidly, with each new generation of devices having more capability, accuracy, and ease of use .
  156. 156. Blocks used  VITA manufactures CEREC Blocs by Sirona andVITABLOCS®Mark II for CEREC®.These blocks are made of feldspathic porcelain.  IvoclarVivadent produces Empress® CAD leucite- reinforced porcelain blocks, as well as IPS e.max CAD blocks of lithium disilicate.  3M™ ESPE™ makes the Paradigm™ C ceramic and Paradigm™MZ100 composite blocks for CEREC®  Zirconia Blocks may also be used  VITA CADTemp
  157. 157. Tooth Preparation  Preparations for specific types of indirect tooth-coloured inlays and onlays may vary because of differences in fabrication steps for each commercial system and variations in the physical properties of the restorative materials. Before beginning any procedure, the clinician should have decided what type of restoration is indicated.
  158. 158.  Preparations for indirect tooth-coloured inlays and onlays basically are meant to provide adequate thickness for the restorative material and at the same time a passive insertion pattern with rounded internal angles and well-defined margins.  All margins should have a 90 degree butt- joint cavosurface angle to ensure marginal strength of the restoration.  All line and point angles, internal and external, should be rounded to avoid stress concentrations in the restoration and tooth, thereby reducing the potential for fractures.
  159. 159.  The carbide bur or diamond used for tooth preparation should be a tapering instrument that creates occlusally divergent facial and lingual walls.  Gingival-occlusal divergence allows for passive insertion and removal of the restoration.  The junction of the sides and tip of the cutting instrument should have a rounded design to avoid creating sharp, stress- inducing internal angles in the preparation.
  160. 160.  Although the optimal gingival-occlusal divergence of the preparation is unknown, it should be greater than the 2° to 5° per wall recommended for cast metal inlays and onlays.  Divergence can be increased because the tooth coloured restoration will be adhesively bonded and as very little pressure can be applied during try-in and cementation.  Throughout preparation, the cutting instruments used to develop vertical walls are oriented to a single path of withdrawal, usually along the long axis of the tooth crown.
  161. 161.  The occlusal step should be prepared 1.5 to 2 mm in depth.  Most composite and ceramic systems require that any isthmus and any groove extension be at least 1.5 mm wide to decrease the possibility of fracture of the restoration.  Facial and lingual walls should be extended to sound tooth structure and should go around the cusps in smooth curves.  Ideally, there should be no undercuts that would prevent the insertion or removal of the restoration. Small undercuts, if present, can be blocked out using a glass-ionomer liner.
  162. 162. Rounded axiopulpal line angle Widened isthmus
  163. 163.  The pulpal floor should be smooth and relatively flat. Following removal of extensive caries or previous restorative material from any internal wall, the wall is restored to more nearly ideal form with a light-cured glass-ionomer liner/base.  The facial, lingual, and gingival margins of the proximal boxes should be extended to clear the adjacent tooth by at least 0.5 mm.These clearances will provide adequate access to the margins for impression material and for finishing and polishing instruments.  For all walls, a 90-degree cavosurface margin is desired because composite and ceramic inlays are fragile in thin cross-section.
  164. 164.  The gingival margin should be extended as minimally as possible because margins in enamel are greatly preferred for bonding and because deep subgingival margins are difficult to record and to isolate properly during cementation.  When a portion of the facial or lingual surface is affected by caries or other defect, it may be necessary to extend the preparation (with a gingival shoulder) around the transitional line angle to include the defect.The axial wall of the shouldered extension should be prepared to allow for adequate restoration thickness.
  165. 165.  When extending through or along cuspal inclines to reach sound tooth structure, a cusp usually should be capped if the extension is two thirds or greater than the distance from any primary groove to the cusp tip.  If cusps must be capped, they should be reduced 1.5 to 2 mm and should have a 90 degree cavosurface angle.
  166. 166.  When capping cusps, especially centric holding cusps, it may be necessary to prepare a shoulder to move the facial or lingual cavosurface margin away from any possible contact with the opposing tooth, either in maximum intercuspal position or during functional movements.  Such contacts directly on margins can lead to premature deterioration of marginal integrity.  The axial wall of the resulting shoulder should be sufficiently deep to allow for adequate thickness of the restorative material and should have the same path of draw as the main portion of the preparation.
  167. 167.  During preparation, stains on the external walls, such as those often left by corrosion products of old amalgam restorations, should be removed. Such stains could appear as black or gray lines at the margin after cementation.  It is especially critical to generously round all line and point angles, internal and external, to avoid areas of stress concentrations that could later lead to fracture of the restoration.
  168. 168. Impressions  Most tooth-coloured indirect inlay/onlay systems require an impression of the prepared tooth and the adjacent teeth as well as interocclusal records, which allow the restoration to be fabricated on a working cast in the laboratory similar to that of cast restorations.
  169. 169. Temporary Restoration  This may be fabricated in the conventional manner, using the direct or indirect method.  Using Acrylic resin or Bisacryl composite materials.  Care must be taken to avoid bonding the temporary restoration to the preparations.  A non-eugenol based temporary cement is recommended for the same. If the temporary phase is expected to last more than 3 weeks, zinc phosphate cement may be used.
  170. 170. CAD CAM Technique  Clinical procedures for CAD/CAM systems such as the CEREC differ somewhat from the procedures previously described.  Tooth preparations for CAD/CAM inlays must reflect the capabilities of the CAD software and hardware and the CAM milling devices that fabricate the restorations.  One example of how preparations are modified when using the CEREC system pertains to undercuts. Laboratory-fabricated indirect systems require the preparation to have a path of draw that allows insertion and removal of the restoration without interferences from undercuts. However, the CEREC system automatically "blocks out" any undercuts during the optical impression.
  171. 171.  Occlusally convergent walls can result in a more conservative preparation along the occlusal aspect, especially when replacing old amalgam restorations, which were prepared with such undercuts for retention.  Care should be taken, however, not to allow excessive undercuts especially at the base of the cusps.These undercut areas eventually will be filled with the composite cement, and these materials lack the properties to act as dentin replacements.  Also, large undercuts may result in undetected internal voids during cementation, which could lead to dramatic failures.The facial and lingual walls of the proximal boxes should be prepared without undercuts and with draw to avoid excessively wide composite cement lines.
  172. 172.  Using the CEREC system, an experienced dentist can prepare the tooth, fabricate an inlay, and deliver it in approximately 1 hour. This system eliminates the need for a conventional impression, temporary restoration, and multiple patient appointments.
  173. 173. Try in and cementation  The try-in and cementation of tooth-coloured inlays / onlays are more demanding than that for cast metal restorations because of:  The relatively fragile nature of the ceramic or composite material,  The requirement of near-perfect moisture control, and  The use of composite cements.  The ceramic or composite inlay is relatively fragile until it is bonded in place with composite cement. Very little pressure should be applied to the restoration during try-in. Because of this fragility, occlusal evaluation and adjustment are delayed until after cementation.
  174. 174.  Optimum Moisture control must be maintained.  After removing the temporary restoration, all the temporary cement is cleaned from preparation walls.  The inlay or onlay is placed into the preparation using very light pressure to evaluate its fit. If the restoration does not seat completely, the most likely cause is an overcontoured proximal surface. Using the mouth mirror where needed, the embrasures should be viewed from the facial, lingual, and occlusal aspects to determine where the proximal contour needs adjustment to allow final seating of the restoration, while simultaneously producing the correct position and form of the contact. Passing thin dental floss through the contacts will reveal the tightness and position, thus signifying to the experienced operator the degree and location of excess contact.
  175. 175.  Articulating papers also can be successfully used to identify overtight proximal contacts. Abrasive disks are used to adjust the proximal contour and contact relationship.  While adjusting the intensity and location of the proximal contacts, successively finer grits of abrasive disks are used to polish the proximal surfaces because they will be inaccessible for polishing after cementation.
  176. 176.  If the proximal contours are not overcontoured, and the restoration still does not fit completely, the preparation should be checked again for residual temporary materials or debris.  If the preparation is clean, internal and/or marginal interferences might also prevent the restoration from seating completely.  Once these interferences have been identified through careful visual inspection of the margins and/or using fit- checker materials, they should be adjusted on the restoration, on the preparation, or both. Fortunately, these interferences are rare because contemporary impression materials and ceramic systems are very accurate, and the laboratory usually applies a die-spacer on the internal aspects of the preparation to avoid difficulties in seating the restoration.
  177. 177.  Marginal fit is verified after the restoration is completely seated. Slight excesses of contour can be removed, if access allows, using fine-grit diamond instruments or 30-fluted carbide finishing burs.  These adjustments are preferably done after the restoration is cemented, to avoid marginal fractures. Most indirect tooth-coloured restorations have slightly larger marginal gaps than comparable gold restorations.
  178. 178. Cementation  For proper adhesive bonding, the internal surface of the inlay/onlay must be treated before cementation.The techniques and materials vary, depending on the specific restorative system used.  For most laboratory-processed composite inlays/ onlays, the resin matrix has been polymerized to such an extent that few bonding sites are available for the composite cement to chemically bond to the internal surfaces of the restoration.
  179. 179.  To improve the bond of the cement to the processed composite restoration, some systems require the use of a solvent to soften the internal surfaces of the restoration before cementation.  Other systems recommend sandblasting or air-abrading the inside of the composite restoration with aluminum-oxide abrasive particles to increase surface roughness and surface area for bonding.
  180. 180.  For ceramic inlays and onlays, hydrofluoric acid is usually used to etch the internal surfaces of the restoration.  Such acid-etching increases surface relief and therefore not only increases the surface area, but also results in micromechanical bonding of the composite cement to the ceramic restoration.  Hydrofluoric acid-etching is usually done by the laboratory.
  181. 181.  However, the clinician should check the internal surface of the restoration to confirm the etching, which is evident by a white- opaque appearance similar to acid-etched enamel.  Chairside ceramic etching is done with a 2- minute application of 10% hydrofluoric acid on the internal surfaces of the inlay/onlay. After etching, the ceramic is treated with a silane coupling agent to facilitate chemical bonding of the composite cement.
  182. 182.  The preparation surfaces are etched and treated with the components of an appropriate enamel/dentin bonding system.Typically, the final step of the bonding system also is applied to the internal surfaces of the restoration previously etched and silanated.  A dual-cure composite cement is mixed and inserted into the preparation with a paddle- shaped instrument or a syringe.  The internal surfaces of the restoration also are coated with the composite cement, and the inlay is immediately inserted into the prepared tooth, using light pressure.
  183. 183.  Excess composite cement is removed with thin-bladed composite instruments, brushes, or an explorer.The operator must be careful not to remove composite from the marginal interface between the tooth and the inlay. The cement is now light-cured from occlusal, facial, and lingual directions for a minimum exposure of 60 seconds from each direction.
  184. 184. Finishing and Polishing For ceramic restorations  Medium- or fine-grit diamond instruments are used initially to remove any excess composite cement back to the margin.  Care must be taken to preserve the glazed surface of ceramic restorations as much as possible. Slender flame interproximally, while larger oval or cylindric shapes are used on the occlusal surface.  After using the fine-grit diamond instruments, 30-fluted carbide finishing burs are used to obtain a smoother finish.
  185. 185. For indirect composite restorations  Finishing may be started with 12-fluted carbide finishing burs instead of diamonds.  Interproximally, a No. 12 surgical blade can be used to remove excess composite cement when access permits.Abrasive strips of successively finer grits also can be used to remove slight interproximal excesses. Much care must be used to avoid damaging the gingiva or the root surfaces when using such instruments interproximally.
  186. 186.  With care and appropriate instrumentation, ceramic restorations can be polished to a surface smoother than glazed porcelain.
  187. 187.  After the finishing and polishing the occlusal contacts are verified and corrected if necessary using a fine grit diamond, followed by 30-fluted carbide finishing burs.  The restoration is then repolished in areas of adjustments made.  Indirect composites may be polished using the same instrumentation and materials used for direct composites.
  188. 188. CAD CAM Restorations  When delivering a CAD/CAM inlay, more adjustments are usually necessary when trying- in, finishing, and polishing.  The original CEREC system milled the occlusal surface relatively flat without any significant surface detail, and did not take into account the opposing occlusion.The newer CEREC 2 and 3 systems are able to mill in occlusal contours in a variety of manners.
  189. 189.  They can extrapolate existing contours beyond the cavo surface margin to the central groove, or they can build the surface up to the level of a scanned wax bite.The neighbouring teeth, in particular the marginal ridges and cusp heights, also can be used as references for the design of the occlusal surface of a CAD/CAM restoration.
  190. 190.  If the preoperative contours of the tooth were satisfactory, the system can reproduce them in the restoration.  When adjusting the occlusion of a CAD/CAM inlay, it may be necessary to use medium-grit diamonds with air-water spray coolant for initial contouring of the occlusal surface, followed by the instrumentation previously discussed for finishing and polishing.
  191. 191. Common Problems and Solutions  The most common cause of failure of tooth- coloured inlays and onlays is bulk fracture. If bulk fracture occurs, replacement of the restoration is almost always indicated.
  192. 192. Repair  Minor defects in indirect composite and ceramic restorations can be repaired with relative ease. Of course, before initiating any repair procedure, the operator should determine whether replacement rather than repair is the appropriate treatment. If repair is deemed to be the appropriate treatment, the dentist should attempt to identify the cause of the problem and correct it if possible. For example, a small fracture due to occlusal trauma may indicate that some adjustment of the opposing occlusion is required.
  193. 193.  For both composite and ceramic inlays, the repair procedure is initiated by mechanical roughening of the involved surface.While a coarse diamond may be used, a better result is obtained with the use of air-abrading or grit-blasting with aluminum oxide particles and a special intraoral device.
  194. 194.  For ceramic restorations, the initial mechanical roughening is followed by brief (typically 2 minutes) application of 10% hydrofluoric acid gel. Hydrofluoric acid etches the surface, creating further microdefects to facilitate mechanical bonding. Although many indirect composites contain etchable glass filler particles, hydrofluoric acid treatment of composites is neither necessary nor recommended. However, a brief application of phosphoric acid may be used to clean the composite surface after roughening.
  195. 195.  The next step in the repair procedure is application of a silane coupling agent. Silanes mediate chemical bonding between ceramics and resins and also may improve the predictability of resin-resin repairs.The manufacturer's guidelines should be followed when using silanes, as they can differ substantially from one particular product to another. After the silane has been applied, a resin-bonding agent is applied and light-cured. A composite of the appropriate shade is placed, cured, contoured, and polished.
  196. 196. Inlay retained bridges
  197. 197. Indications:  Abutment teeth with fillings  Replacing 1 or 2 teeth in the premolar, molar region  Metal-ceramic  All-ceramic  Fiber –reinforced composite
  198. 198. Contraindications:  Pontic span too large  Excessive parafunctions  Clinical crown too short  Weakend periodontium  Occlusal anomalies  Abutment teeth tilting  Poor oral hygiene
  199. 199.  Advantages:  Less destructive to tooth structure  Cavities, fillings involved in preparation  Good esthetics  Fixed restoration  Marginal finishing line easy to clean- preservation of the periodontium  Disadvantages:  Only 1 or 2 missing teeth-short pontic span
  200. 200. Preparation for an inlay-retained bridge Apply Primer to the enamel and dentin and disperse
  201. 201. Etch the pressed inlay-retained bridge with IPS Ceramic Etching gel for 20 sec., rinse and silanize. Fill the bridge with Cement and remove excess
  202. 202. IPS e.max ZirPress on Zirconium Oxide Inlaybridge
  203. 203. Strength  Noble Metal Alloys  High Noble  Yield Strength: 270-600 Mpa  Noble  Yield Strength: 260-1145 MPa  Base Metal Alloys  Yield Strength: 644-710 Mpa  Tensile Strength: 700-970 MPa
  204. 204.  Ceramics  Heat Pressed  Flexural Strength: 121-350 Mpa  Feldspathic  Flexural Strength: 60 Mpa  CAD/CAM  Flexural Strenght: 105-900 MPa  Composites  Direct and Indirect  Flexural Strength: 60-180 MPa  Amalgam  Compressive Strength: 227-526 MPa
  205. 205. Review of literature  In a dental practice, 2328 ceramic inlays were placed in 794 patients.The restorations were manufactured chairside using CEREC technology and adhesively inserted at the same appointment.  The probability of survival was 95.5% after 9 years; 35 CEREC restorations were judged as failures.  In a clinical follow-up light-microscopic examination of 44 randomly selected restorations, an average composite joint width of 236.3 microns was found. 45.1% of the restorations exhibited a perfect margin, and 47.4% of the investigated joint sections showed underfilled margins. PosseltA, KerschbaumT. Longevity of 2328 chairside CEREC inlays and onlays. Int J Comput Dent. 2003; 6(3): 231 – 248.
  206. 206.  This follow-up study examined the performance of CEREC inlays and onlays in terms of clinical quality over a functional period of 10 years.  Of 200 CEREC inlays and onlays placed in a private practice between 1989 and early 1991, 187 restorations were observed over a period of 10 years.The restorations were fabricated chairside using the CEREC-1 computer-aided design/manufacturing (CAD/CAM) method andVita MK I feldspathic ceramic.An adhesive technique and luting composite resin were used for seating the restorations. After 10 years, the clinical performance of the restorations was evaluated using modified USPHS criteria.The results were used to classify success and failure.  RESULTS:The success rate of CEREC inlays and onlays dropped to 90.4% after 10 years. A total of 15 (8%) failures were found in 11 patients. Of these failures, 73% were caused by either ceramic fractures (53%) or tooth fractures (20%).The reasons for the remaining failures were caries (20%) and endodontic problems (7%). The three-surface CEREC reconstructions were found to have the most failures. OttoT, De Nisco S. Computer-aided direct ceramic restorations: a 10-year prospective clinical study of CEREC CAD/CAM inlays and onlays. Int J Prosthodont. 2002; 15(2): 122 – 128.
  207. 207.  29 clinical reports were identified in the search.The systematic analysis reduced the focus of review to 15 studies. The data available establishes ceramic intra-coronal restorations machined by the CEREC System as a clinically successful restorative method with a mean survival rate of 97.4% over a period of 4.2 years.The review also highlights the reasons and the rates of failure for this type of restoration.The predominant reasons for failures are fracture of the ceramic, fracture of the supporting tooth, postoperative hypersensitivity and wear of the interface lute.  SIGNIFICANCE: Machinable ceramics, as used by the CEREC System provide a useful restoration with a high success rate. These restorations are color stable and wear at a clinically acceptable rate.Wear of the luting composite on occlusal surfaces leads to the phenomenon of submargination. Ceramic fracture, wear at the interface and post-operative hypersensitivity remain a problem which requires further investigation. Martin N, Jedynakiewicz NM. Clinical performance of CEREC ceramic inlays: a systematic review. Dent Mater. 1999; 15(1): 54 – 61.
  208. 208.  CEREC or IPS Empress ceramic inlays, Arabesk or Charisma F resin-based composite (RBC) restorations were compared in this study.  There was no significant difference (P > 0.05) between the mean values of the sound teeth (2,102 N) and the teeth with the CEREC ceramic inlays (2,139 N). However, both groups demonstrated a significant difference (P < 0.05) when compared with the teeth with IPS Empress ceramic inlays (1,459 N) and Arabesk RBC restorations (1459 N). No significant differences were found between the last two groups. Molars restored with Charisma F composite restorations (1,562 N) revealed no significant difference when compared with all other groups including controls (P > 0.05).  A stabilization of molars is possible by means of an adhesive restoration in the form of an “internal splinting” regardless of the restorative material used. Bremer BD, GeurtsenW. Molar fracture resistance after adhesive restoration with ceramic inlays or resin-based composites. Am J Dent. 2001; 14(4): 216 – 220.
  209. 209.  Al-Hiyasa et al in their study to compare the wear of teeth against four dental porcelains and gold concluded that gold was the least abrasive. And that machinable ceramics significantly less abrasive and more resistant to wear than the conventional aluminous and bonded porcelains. Al-Hiyasat AS, SaundersWP, Sharkey SW, Smith GM, GilmourWH. Investigation of human enamel wear against four dental ceramics and gold. J Dent. 1998; 26(5-6): 487 – 495.
  210. 210.  An in vitro study to evaluate the fracture load of zircon frames veneered with a polymer glass holding box inlay-retained fixed partial dentures was conducted by Ohlmann et al.  And they concluded that Polymer veneered FPDs withY-TZP frames showed acceptable fracture resistance values, but they cannot yet be unreservedly recommended for clinical use. Fracture values for CAD/CAM manufacturedY- TZP frames combined with a press ceramic deserve further clinical investigation. Brigitte Ohlmann 1†, Olaf Gabbert 1, Marc Schmitter 1, Herbert Gilde 1 and Peter Rammelsberg. Fracture resistance of the veneering on inlay-retained zirconia ceramic fixed partial dentures. 2005,Vol. 63, No. 6, Pages 335-342 Acta Odontologica
  211. 211.  Wolf compared the margin quality of titanium and high gold inlays and found that the margins of titanium restorations were acceptable clinically but high gold restorations had better marginal adaptation. B.Wolf Margin quality of titanium and high-gold inlays and onlays — a clinical study Dental Materials,Volume 14, Issue 5, Pages 370-374
  212. 212.  A clinical study on Zirconia based ceramic inlay retained FPDs inferred that on’y 1o% of the bridges were unacceptable after a 2 year period of study. And 80% of the restorations were acceptable in accordance with the US public health criteria.  Within the limitation of this study, it was concluded that Zirconia based ceramic inlay retained fixed partial dentures showed a satisfactory clinical performance over 24 months period. Mahmoud Abdul Salam Mohamed Shakal CLINICAL EVALUATIONOF ZIRCONIA BASED CERAMIC INLAY RETAINED FIXED PARTIAL DENTUREVolume (55), Number (3.1), Jul 2009
  213. 213.  Niek et al reported a survival for composite resin of 91.7% in 5 years and 82.2% in 10 years.  For amalgam the survival rate is 89.6% at 5 years and 79.2 % at 10 years Dental materials 2007; 23: 2-8
  214. 214.  A study was done to evaluate the clinical performance of bonded leucite reinforced glass ceramic inlays and onlays after 8 years Conclusions:  Marginal integrity was decreased at the end of 8 years  Surface roughness was increased  No significant influence was attributed to the size of the inlay  The absence of enamel in proximal boxes did not have any influence on the marginal performance or secondary caries of the inlays and onlays. Dent Materials 2005;21:262–71
  215. 215.  Chipping mainly occurred in areas having been subjected to rotary occlusal adjustment  No statistically significant correlation between dimensions of the inlay and fractures were observed  It was concluded that IPS Empress inlays demonstrated to be successful even in large defects. Neither the absence of enamel margins nor cuspal replacement affected the quality of the restorations. Dent Materials 2005;21:262–71
  216. 216.  Various long term studies upto 15 years have shown that ceramic inlays made of prefabricated Cerec Mk block ceramic had a signifcantly higher survival rate than laboratory fired ceramic inlays. Chicago :Quintessence 2006:65-72
  217. 217.  A study was done to examine the performance of Cerac inlays and onlays in terms of clinical quality over a functional period of 10 years  Three surface inlays had significant lower survival rates  Premolars have slightly lower risk than molars  Higher risk of failures were seen in male patientsIn most cases facture occurred at thinnest region of the inlay (isthmus fracture) or at the marginal ridges  Bruxism should be considered a risk group with regards to Cerec restorations Int J Prosthodont 2002;15:122-128
  218. 218.  A study was done to compare 4 types of inlays direct composites, Indirect composites ( Estilux), Direct ceramic ( cerec system), Indirect ceramic (Vita Dur N)  The survival rate for inlays without repair was 80% for cerec inlays , 66.9% forVita Dura N , 55.5% for Estilux and 66.7% for direct composites  No significant differences in surface textures  No significant differences in color match but marginal discoloration was found in composite restorations  Main reason for failures ofVita Dura N was fracture of the restorations and for composites it was secondary caries and pulpal reactions Quintesssence Int 2006;37: 139-144
  219. 219. References: 1. Shillingberg, H.T. Jr et al. Fundamentals of Fixed Prosthodontics, 3rd edn. 2. Shillingberg, H.T. Jr et al. Fundamentals of Tooth Preparation. 3. Rosensteil, Land, Fujimoto. Contemporary Fixed Prosthodontics. Fourth Edition. 4. Sturdevant's Art and Science of Operative Dentistry. Fifth edition 5. G. F. Kantorowicz. Inlays, Crowns and Bridges. 3rd Edition. 6. Cowell, Curson. Inlays, Crowns and Bridges. 4th Edition.
  220. 220. 7. Posselt A, KerschbaumT. Longevity of 2328 chairside CEREC inlays and onlays. Int J Comput Dent. 2003; 6(3): 231 – 248. 8. OttoT, De Nisco S. Computer-aided direct ceramic restorations: a 10-year prospective clinical study of CEREC CAD/CAM inlays and onlays. Int J Prosthodont. 2002; 15(2): 122 – 128. 9. Martin N, Jedynakiewicz NM. Clinical performance of CEREC ceramic inlays: a systematic review. Dent Mater. 1999; 15(1): 54 – 61. 10. Bremer BD, GeurtsenW. Molar fracture resistance after adhesive restoration with ceramic inlays or resin- based composites.Am J Dent. 2001; 14(4): 216 – 220. 11. Al-Hiyasat AS, SaundersWP, Sharkey SW, Smith GM, GilmourWH. Investigation of human enamel wear against four dental ceramics and gold. J Dent. 1998; 26(5-6): 487 – 495.
  221. 221. 12. Brigitte Ohlmann, Olaf Gabbert, Marc Schmitter, Herbert Gilde and Peter Rammelsberg. Fracture resistance of the veneering on inlay- retained zirconia ceramic fixed partial dentures. 2005,Vol. 63, No. 6, Pages 335-342 Acta Odontologica 13. B.Wolf Margin quality of titanium and high-gold inlays and onlays — a clinical study Dental Materials,Volume 14, Issue 5, Pages 370-374 14. Mahmoud Abdul Salam Mohamed Shakal Clinical Evaluation Of Zirconia Based Ceramic Inlay Retained Fixed Partial Denture.Volume (55), Number (3.1), Jul 2009 15. Dental materials 2007; 23: 2-8 16. Dent Materials 2005;21:262–71 17. Chicago :Quintessence 2006:65-72 18. Int J Prosthodont 2002;15:122-128
  222. 222. Thank you for your kind attention